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Questions tagged [rf]

Short for Radio-Frequency. Frequencies at which radiation (intentional or not) plays a role. Typically associated with wireless communications, but also relevant for high-speed PCB design.

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Schematic diagram of a double-balanced Gilbert cell mixer

For the following gilbert cell circuit, I have few questions. I understand that R1 to R4 as well as M1 to M6 are parts of the double-balanced differential topology which helps to eliminate the DC ...
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1answer
48 views

Is it parallel or series

In the figure below, an RLC circuit, the author in the book says, that the resonant circuit sees Rs and RL to be parallel so he combined them (R total = the parallel sum of Rs and RL), is it right ...
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1answer
51 views

“RF energy harvesting” Can rf transmitter be a rf signal generator?

I'm trying to build an rf energy harvester. But having some problem. The harvester should collect the 915Mhz signal. Can I use 915Mhz rf transceiver + 915mhz amplifier as the rf signal source? How ...
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3answers
141 views

How to find the frequency of any device?

Are there devices which can figure out at what frequency every device transmitting radio frequencies operate at precisely? Say from a high of 2.4 GHz microwave to a low of 402 Hz pacemaker.
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11 views

Single Ended DAC to Differential Input Modulator

I'm trying to drive a differential input IQ modulator (LT5571) with a single ended DAC (MCP4912) for modulation of a narrow band signal (~10kHz max). Because of the nature of the low frequency ...
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49 views

What transmissions technology has the largest range, with the lowest power consumption? [on hold]

Perhaps this isn't the right question (or right place to ask it) but I am building a fixed wing "drone" and I would love at least 1 way communication (from the drone to a station) for the majority of ...
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4answers
2k views

Can I run 125kHz RF circuit on a breadboard?

I was wondering if making a low frequency RF circuit on a breadboard is viable.
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0answers
32 views

Pair 433 MHz RF devices [on hold]

I need to build system "turn on lamp with wireless PIR sensor". I'm planning to buy 433 MHz PIR sensor and somehow pair it with 433 MHz relay. But how to pair them? How to get codes from transmitter ...
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1answer
31 views

Cutoff or Corner Frequency for Coax Cable

I'm trying to understand better what the significance of the cutoff frequency for coax cables is. I have a case where a cable is considered for use at frequencies up to 3% higher than the manufacturer'...
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24 views

RF device connection issue

I have a surface acoustic wave based separator device built on piezoelectric (PZT) substrate and this is mounted on a PCB for the external connection as you can see from the picture. When I was ...
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2answers
73 views

Smith chart of λ/4 Transmission Line

I came across the following slide on power combiner circuit and I have questions about it. Why traverse across the upper half circle ? Why "ZT-line is the geometric mean of Zout and Zin." ?
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0answers
48 views

Audio PWM over Radio [on hold]

I'm working on a project in which I must send audio over RF such that remote speakers can pick up the signal around a house/apartment. The goal is to broadcast music from a single device somewhere in ...
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17 views

EN 300 328 Receiver (RX) Blocking | BLE DTM Implementation with Signaling Analyzers?

We are working through a Nordic NRF 52832 certification, and are getting the device CE tested. We are running into some issues getting our device connected to the R&S CMW 500 signaling analyzer ...
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91 views

First PCB project design critique requested (RF) EDITED

This is my first ever RF PCB project and it'd be great to receive some guidance to make this project 'first-time-right'. It's purpose is to transmit and receive signals at two different frequencies: ...
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1answer
56 views

In actual OFDM trasmitter, is the stepwise waveform after IFFT put on the carrier as it is?

I simulated OFDM on MATLAB,though,the spectrum of it is not white(flat shape). Why? IFFT circuit of actual transmitter uses higher IFFT order than the count of subcarriers? P.S. I simulated with the ...
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0answers
20 views

Realizing a prototype filter in ADS or any other simulator

I'm trying to design a stub-filter, and I'm stuck on realizing the filter design using Richard's transformations and Kuroda identities. I'm building a 5th order Chebyshev LP-filter for 2.6 GHz pass-...
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50 views

Is there any 433mhz rf transmiter/module/transceiver can work at 1v voltage or lower? [closed]

I am finding this kind of transmitter but it seems there is no such kind of components. Does anybody know? Thanks Because I want to use a msp430l092 which work can at 0.9v at least. Combining it ...
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1answer
43 views

What should be assumed regarding the upper frequency of sma connectors

There are infinitely many sellers of sma connectors of various kind in ebay or other stores. This one is an example. But they very seldom specify what is the maximum frequency at which the device can ...
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0answers
41 views

Microphonic SAW transmitter?

I built this very simple SAW transmitter, with a simple "spring" antenna for the right frequency. To test it, I tuned a portable receiver to around 433.92Mhz and fine tuned it until I heard silence. ...
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0answers
25 views

Need guidelines with creating chip module footprint [closed]

I am trying to design my own RF PCB using online pcb-editor Easyeda. My circuit uses RF module cc1101. I couldn't find matching PCB library for my module so I decided to create one myself. I basically ...
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0answers
31 views

Reactance of a dipole antenna

I am interested in calculating the input impedance \$Z_{in}=R_{in}+jX_{in}\$ of a dipole antenna numerically. However, I am unsure how I would compute the imaginary part of the impedance (\$X_{in}\$). ...
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1answer
17 views

Conversion Gain Definition for DSB-SC Upconversion

If I multiply a baseband signal \$A cos(C\omega t)\$ and a carrier signal \$B cos(D\omega t)\$, the result is \$\frac{AB}{2} [cos(C-D)\omega t+cos(C+D)\omega t]\$, which is a double sideband, ...
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1answer
32 views

I cannot find information about some chips in 3 stage LNA circuit

Hi, here you can see 3-stage LNA circuit. I want to know information about two chips(6 pins) with R8 mark at the top. Also, 4 chips with D4 mark with 3 pins at right side. Is there anyone who has a ...
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0answers
39 views

What kind of Modulation? Who transmits on 850 MHz (LTE-Uplink or GPRS?)?

Hey, I found an interesting Signal on 850MHz (in Germany). It is not symmetric and very strong (relative to many others due to bad antennas). On the right side the bandwith is permanently used, on the ...
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0answers
28 views

Cheap RF 433.92MHz design, PCB track antenna [duplicate]

I'm doing a RF remote control project using a PCB with microcontroller and with simple onboard antenna layout as transmitter and a 433.92MHz receiver RWS-371F-6 model. Here is the datasheet of the ...
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2answers
112 views

160MHz Ambient Office Noise?

I've got a shielded tent in our office and I see one ambient element I don't have a good explanation for. We see some ambient noise at 700MHz - 800MHz which I guess is cell-band noise. But there is ...
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103 views

On purpose shorted capacitor in schematic

I've come across this schematic from an RF device where I've spotted some weird configuration of capacitors. There are, all around the schematic, some shorted capacitors which I can't figure out what ...
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1answer
53 views

RF Design / Calculations - 433.92MHz, PCB antenna, values of capacitors

I'm doing a RF remote control project using a PCB with microcontroller and with simple onboard antenna layout as transmitter and a 433.92MHz receiver RWS-371F-6 model. Here is the datasheet of the ...
6
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2answers
116 views

Tube transmitter tuning

I am trying to tune/tweak/repair this transmitter for a friend of mine. It is oscillating, and it has rf power on the antenna, but it just doesn't seem as "strong" as it should be. The diagram says ...
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3answers
51 views

Minimizing reflection coefficient of a low-pass filter

I'm trying to figure out (with not a lot of success) as to what I need to consider when I want to minimize reflection coefficient below a certain point. I'm trying to design a low-pass shunt stub ...
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1answer
29 views

S21 VNA Connector & Cable Loss?

I've tuned plenty of RF devices using my VNA for impedance matching. But I've never done an S21 measurement. I have a shielded tent with some connectors and SMA cables that are going to introduce ...
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1answer
44 views

Tube transmitter plate current meter question

Can I install the mA meter in this schematic directly in the circuit? This is the high voltage plate supply and there is RF on it. The diagram doesn't specify if there is any circuitry to adapt the ...
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2answers
70 views

RF Antenna Matching circuit and PCB design for 868 MHz SigFox device

I'm designing a Sigfox sensor device based on WISOL/SFM10R1 a SigFox verfied module by WiSOL and Atmega328. I need to understand the parameters for 868 MHz RF Antenna Matching circuit and PCB trace ...
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1answer
65 views

How can I design a high speed RF peak detector?

The diode-capacitor solution would not work in my application because the operating frequency of my circuit is about 1.4GHz. So what is an alternative solution that would work in such high frequencies?...
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1answer
32 views

Phased array receiver circular polarization

In a phased array system, what will have to change in a receiver's architecture if it needs to work for both linear and circular polarization? I saw in one article it is said "Supports automatic ...
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2answers
78 views

How same frequency signal with different power are produced?

My router have settings to configure transmission power and as i know energy of a signal is given by $$ E = h\nu $$ where \$E\$ is the energy of the signal, \$h\$ is Planck's constant, \$\nu\$ is ...
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1answer
57 views

(Antenna impedance matching) How to find the load impedance

I'm working on a project that requires impedance matching and I'm going to match a 50 Ω antenna to a RF amplifier SST12LP22. However, I'm not sure how can I get the impedance of the amplifier from the ...
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1answer
86 views

In this Foster Seeley discriminator, what is the purpose of capacitor C3?

I understand the whole circuit, except for the use of capacitor 3. What's its purpose in here?
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63 views

How does this transmitter work/how to tune it?

I have used a few 433MHz ASK transmitters. They're cheap, readily available, and work reasonably well. Based on this application note from Murata I tried to build my own. I replaced the NE68030 ...
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2answers
56 views

How does this simple FM slope detector work?

I understand what happens from the diode onwards, it's a rectifying amp and a low pass filter that filters any unwanted frequencies from the carrier, but what is going on in terms of voltage between ...
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1answer
115 views

How to measure radio signal strength

I am building several types of radio antennas, and I would like to test which is the most effective. I am wondering: What is the best way to measure the strength of the received signal? It is at ~...
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1answer
53 views

designing Low-Pass Transmission Line Stub Filter

I'm trying to design a Low-Pass transmission line stub filter, and I have a few question regarding it. I'm rather new to RF-circuit design, so please bear with me. If my desired specs include the ...
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1answer
23 views

Absorber effect on EM RF pattern

If I have an omnidirectional antenna and put a perfect reflector plane near it (in the near field), it will obviously change its radiation pattern in the direction opposite the reflector. ...
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1answer
166 views

Sub 1 GHz communication - long range at 500kbps. Is my range estimate roughly correct?

When researching long range medium bitrate RF comms I came across the TI range. The TI CC1201 transceiver claims -97dBm sensitivity at 500-1000kbps. If the system is on the 868MHz band which is ...
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1answer
28 views

How to link 3 RF transceivers to 1 antenna

I'm not an RF designer, so excuse the newbie question: How would I link three transceivers, say WiFi and two separate bluetooth transceivers, to a single antenna. I have found a 3-way combiner ...
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0answers
25 views

What causes the fail-safe bit to be set in the SBUS protocol?

What causes the fail-safe bit to be set in the SBUS protocol? I know that the when the link between the transmitter and receiver is lost, the fail-safe bit is set, however, what constitutes a 'lost ...
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1answer
41 views

Bitstream autocorrelation? - comparing two bitstreams - BER?

I am sending a PN9 sequence from a sender to a receiver and want to compare the received bitstream (RB) to the sent one (SB). I am assuming that the transmission will get distorted and want to somehow ...
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1answer
81 views

What is the fastest SiC MOSFET?

I would like to know what is the fastest SiC FET greater than or equal to 10A in a TO-247-3 package. Currently I am using a C2M0280120D. My switching speed is 7 MHz. I want to know if there is a ...
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3answers
196 views

Homemade Faraday Cage?

I'm working in an office with a Wi-Fi router, desktop, and a few cell phones making RF noise. I have an 8 feet long by a 3-feet wide table, and I have an Aaronia BICOLOG 30100 + spectrum analyzer + ...
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1answer
55 views

Drivers for high power RF switches

I am currently working on an RF project and using a high power RF SPDT switch. The control voltages of this switch are between 0V/-40V. If the control voltage is 0V, then the corresponding path is ON ...